Module 7 - Vision, Proprioception & Touch

What are rods?

Photoreceptors that are more numerous in the retina, do not detect colour, and are specialized for dim light and detecting movement.

What are cones?

Photoreceptors that function best in bright light, specialized for colour vision and visual acuity — concentrated in the fovea. They are essential for detecting fine details and distinguishing colours.

What is the fovea?

The central area of the retina where cones are concentrated, allowing the clearest and sharpest vision.

What is the optic chiasm?

The point where some fibers from each optic nerve cross — visual information from the left visual field goes to the right hemisphere and vice versa.

What is the focal visual system?

The visual system involving the fovea and cones — functions to identify objects in the central visual field.

What is the ambient visual system?

The visual system functioning largely at a subconscious level — provides information about spatial location, orientation, balance, and locomotion.

What is optic flow?

The flow of objects and surfaces in our visual field as we move — informs how quickly we are approaching them and guides locomotion.

What is time to contact (Tau)?

The amount of time until an object will make contact, determined from the expansion of the object on our retinas as it approaches.

What is proprioception?

The continuous flow of sensory information from receptors in muscles, tendons, joints, and the inner ear regarding movement and body position.

What are muscle spindles?

Proprioceptors in the muscle belly that detect how much and how fast a muscle's length is changing.

What are Golgi Tendon Organs?

Proprioceptors at the muscle-tendon junction that convey information about contraction intensity and protect against excessive tension.

What are cutaneous receptors?

Receptors in the skin that provide tactile information such as light touch, pressure, vibration, warmth, and pain.

What do Meissner's corpuscles detect?

Light touch and changes in texture — found in hairless (glabrous) skin, respond to low-frequency stimulation.

What do Merkel's corpuscles detect?

Sustained pressure and fine spatial detail — important for discriminative touch.

What do Pacinian corpuscles detect?

Deep pressure and vibration — respond to rapid pressure changes.

What do Ruffini corpuscles detect?

Skin stretch and sustained pressure — also contribute to proprioception and warmth detection.

What do free nerve endings detect?

Pain, temperature, and crude touch — primarily nociceptors and thermoreceptors.

What did Lee and Aronson (1974) find?

Infants swayed or fell in the direction of a moving room's walls even though the floor didn't move — 82% of responses were positive, showing vision dominates over mechanical proprioception for postural control in infants.

What did Baker and Cinelli (2014) find?

Previously concussed athletes (cleared to return to play) showed variable decision-making in a gap-passing task, attempting gaps as small as 1.0x shoulder width vs. 1.4x for healthy controls — suggesting subtle visuomotor deficits persist after concussion.

What did Savelsbergh et al. (1993) find?

Catchers timed maximal hand opening based on retinal expansion (time to contact). When vision was removed earlier (300 ms before contact), grip timing and aperture accuracy declined — highlighting vision's role in interceptive skills.